Non-Equilibrium Radiative Force

red ball  Radiation Pressure from a hot-plate can in principle counteract Casimir attraction

    Hieronymus-Bosch,-The-Last-Judgement.-Central-Panel-with-Detail-of-Heaven

yellow ball Around room temperature, this is for distances exceeding 7 microns; somewhat large for practical applications,

while at short separations "near-field effects" due to evanescent waves lead to non-classical behavior.

red ballAt short separations "near-field effects" due to evanescent waves modify classical "Stefan-Boltzmann" law:

yellow ball "Surface Phonon Polaritons Mediated Energy Transfer between Nanoscale Gaps,"

S. Shen, A. Narayanaswamy, & G. Chen, Nano Lett. 9, 2909 (2009)

 Breaking the law, at the nanoscale (MIT news, July 29, 2009)

 

yellow ball Heat transfer between plates diverges at short distances due to evanescent waves (tunneling).

red ballA generalized scattering approach enables computation of Casimir forces, as well as radiation and heat transfer,

in non-equilibrium steady states.

yellow ball "Nonequilibrium Electromagnetic Fluctuations: Heat Transfer and Interactions,"

M. Krüger, T. Emig, and M. Kardar, Phys. Rev. Lett. 106, 210404 (2011)

Rytov (1959):      "Fluctuational QED"

yellow ball Fluctuating currents in each object are related to its temperature by a fluctuation-dissipation condition:

yellow ball The EM field due to thermal fluctuations of one object is related to overall Green's function by:

yellow ball The overall fluctuations with many objects at different temperatures is then given by:

yellow ball From EM correlations follow the stress tensor and the Poynting vector, hence forces and radiation.

red ball  Example of non-equilibrium Casimir levitation:

yellow ball A hot microsphere can levitate on top of a cold plate.

yellow ball If it cools down (including heat transfer) the sphere will fall down.